Okay this perhaps maybe isn’t a problem so much of fvwm but of feh and Esetroot that I’ve tried.
But every time I set a background, using either of these two options, I can get a background up but my computer freezes up and I have to exit out of X and restart only to have just a black screen again.
I’m not sure why it would be freezing up so badly.
Do you get the same problem using fvwm-root or FvwmBacker?